Rapid Electrochemical Impedance Spectroscopy for Protein Detection in Lab-on-a-Chip Devices

Lab-on-a-Chip devices form an ever-growing segment of the IVD market, and there is a pronounced need for reliable, rapid detection methods for various biomarkers, especially label-free methods. Electrochemical impedance spectroscopy (EIS) in liquids means the determination of passive electrical properties of ingredients in a continuous or segmented flow of fluids. More specifically, it means label-free discovery, counting and characterization of particles, mostly concentrations of various ionized molecules in chemical solutions or biological particles in fluids. We present results in rapid solution impedance spectroscopy to detect protein interactions (antibody-antigen) in human serum. The experimental setup was based on screen-printed electrodes (Dropsens DRP-C220AT) and cuvettes (Brandtech 7592 00), and the serum was buffered in PBS. Two different serum-antibody mixtures were created and impedance spectra recorded over 15 minutes to determine whether the system was capable of discerning solution compositions. Significant shifts in impedance magnitude and phase were detected in the 10 Hz-100 kHz range, with a clear difference between peaks for both solutions. Although in the described experiment, the solution was static, this setup could be adapted to be part of a flow cell.